CN1663277A - Robust method for achieving audio/video synchronization in MPEG decoders in personal video recording applications - Google Patents

Abstract

A receiver for receiving an MPEG encrypted transport stream and outputting audio and video signals comprising: a decryptor adapted to receive and decrypt the encrypted transport stream; a de-multiplexer adapted to convert the decrypted transport stream to audio and video elementary streams and to change the values in presentation time stamp and decoding time stamp fields of each packet of the audio and elementary streams to match the time of a receiver record clock; a storage sub-system adapted to store the audio and the video elementary streams and to change the values in the presentation time stamp and decoding time stamp fields of each header of the audio and video elementary streams to compensate for the amount of time the audio and video elementary streams are stored; and audio and video decoders to decode the audio and video elementary streams respectively.

Description

A Robust Method for Audio/Video Synchronization in MPEG Decoders in Personal Video Recording Applications

The present invention relates to the field of recording and playback of broadcast streams; in particular, an apparatus and method for synchronizing the decoding and presentation of video and audio from broadcast streams in a video recording environment.

This application relates to the co-inventors and subject matter of a co-pending application entitled "Robust Method For Recovering A Program Time BaseIn MPEG-2 Transport Streams And Achieving Audio/Video Synchronization" (for recovering MPEG-2 Procedural Timebase and a Robust Method for Implementing Audio/Video Synchronization), S/N 09/967,877, which is hereby fully incorporated by reference.

The Moving Picture Experts Group Phase 2 (MPEG-2) standard is a digital audio/video (A/V) compression standard used in a variety of audio/video distribution systems, including, for example, digital satellite systems ( DSS) broadcast. The MPEG-2 transport standard, ISO 13818-1, requires broadcasters to transmit Program Clock Reference (PCR) time stamps in periodic slots within a multiplexed stream of audio and video packets. This program clock reference time stamp is called the system clock reference (SCR) in the DSS program stream, which carries a strict relationship to one or more system time clocks (STC) within the MPEG-2 encoder producing the broadcast stream, Therefore it can be used to replicate the encoder's system time clock in the decoding device. In addition, each audio and video packet multiplexed into an MPEG-2 broadcast stream includes a decoding time stamp (DTS) and a presentation time stamp (PTS), which identify the time relative to the program clock reference at which the packet must The two markers are respectively decoded and represented by the decoding device for display.

The implementation of Personal Video Recording (PVR) involves storing broadcast programs on a storage medium and then playing them. If the program is stored entirely as an MPEG-2 stream and injected for playback at the original broadcast bit rate, timing information is maintained to allow the delayed program to use the same audio/video synchronization mechanism as the live broadcast. The full storage of the MPEG-2 stream requires an excessive amount of memory, however, if the MPEG-2 stream is altered or compressed by dropping the procedure or if the program is altered or compressed by dropping sub-channels, the memory requirement is reduced but the PCRs arrive at critical timing. Storing only the audio elementary stream (AES) and video elementary stream (VES) also reduces memory requirements at the expense of PCR arrival time. During playback, the loss of PCR arrival times causes serious audio/video synchronization problems, manifested as noise, interruptions, or pauses in the audio/video representation.

A first aspect of the present invention is a receiver for receiving an MPEG encrypted transport stream and outputting audio and video signals, comprising: a decryptor adapted to receive the encrypted transport stream, to decrypt the encrypted transport stream and output A decrypted transport stream; a demultiplexer adapted to receive the decrypted transport stream, to convert the decrypted transport stream into an audio elementary stream and a video elementary stream, and to change the audio elementary stream and the video elementary stream The value in the Representation Timestamp and Decoding Timestamp fields of each header of each packet of the stream to match the time of the receiver's recording clock and suitable for outputting audio elementary streams and video elementary streams; the storage subsystem, suitable for receiving and stores audio elementary streams and video elementary streams, and is adapted to vary the values in the presentation time stamp and decoding time stamp fields of each header of each packet of the audio elementary streams and video elementary streams to compensate for the the amount of time the stream is stored in the storage subsystem; an audio decoder adapted to receive and decode an audio elementary stream and adapted to output an audio signal; and a video decoder adapted to receive and decode a video elementary stream and adapted to output a video signal .

A second aspect of the present invention is a receiver for receiving an MPEG encrypted transport stream and outputting audio and video signals, comprising: a decryptor adapted to receive the encrypted transport stream, decrypt the encrypted transport stream and output the encrypted Decrypted transport stream; selector, adapted to receive a decrypted transport stream, adapted to select packets associated with one or more procedures, and adapted to create a partial transport including only packets associated with one or more procedures, suitable for suitable for adding time stamps to each packet in a partial transport stream based on the receiver recording clock, and suitable for outputting the partial transport stream; a storage subsystem, suitable for receiving and storing the partial transport stream; a demultiplexer, suitable for receiving Partial transport streams, suitable for converting partial transport streams into audio elementary streams and video elementary streams, suitable for changing the values in the presentation time stamp and decoding time stamp fields of each header of each packet of audio elementary streams and video elementary streams , to compensate for the amount of time a portion of the transport stream is stored in the storage subsystem; an audio decoder, adapted to receive and decode an audio elementary stream and output an audio signal; and a video decoder, adapted to receive and decode a video elementary stream and output a video Signal.

A third aspect of the present invention is a method for synchronizing audio and video in an MPEG decoder, the method comprising: decrypting a transport stream; demultiplexing the transport stream; Extract the value of the first program clock reference field in the header of a packet; demultiplex the transport stream into an audio elementary stream and a video elementary stream; compare the current time with the first program clock reference in the packet header of the decrypted transport stream The difference between the field values is added to each Presentation Time Stamp field and each Decoding Time Stamp field of each header of each packet in the audio and video elementary streams associated with the program to be stored, where the decrypted transmission The packets in the stream are associated with the program to be stored; the audio and video elementary streams are stored; the difference between the time when the audio and video elementary streams are stored and the playback time when the audio and video elementary streams are read from memory is added to Each presentation time stamp field and each decoding time stamp field of each header of each packet in the audio and video elementary streams; decoding the audio and video elementary streams.

A fourth aspect of the present invention is a method for synchronizing audio and video in an MPEG decoder comprising: decrypting a transport stream; selecting packets associated with one or more programs and establishing Partial Transport Stream of program-dependent packets; adds a timestamp based on the current recording time to each header of each packet in the partial transport stream; stores the partial transport stream; reads the partial transport stream; demultiplexes the partial transport stream For audio elementary streams and video elementary streams; add the difference between the value of the first program clock reference field in the header of the packet in the decrypted transport stream and the current time to each header of each packet in the audio and video elementary streams Each represents a time stamp field and each decodes a time stamp where packets in the decrypted transport stream are associated with programs to be stored; decodes audio and video elementary streams.

The characteristics of the invention are set out in the appended claims. However, the invention itself will be best understood by reference to the following detailed description of illustrative embodiments, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a receiver according to a first embodiment of the present invention;

FIG. 2 is a schematic diagram of a receiver according to a second embodiment of the present invention;

Figure 3 is a graph illustrating the relationship between playback and recording STC and PTS of a receiver modified in accordance with the present invention during recording; and

Fig. 4 is a graph illustrating the relationship between receiver playback and recording of STC, original PTS and modified PTS according to the present invention during trick-to-normal play.

For the purposes of the present invention, it is understood that, unless otherwise specified, the term transport stream (TS) refers to the MPEG TS, the term program stream (PS) refers to the MPEG PS, and the term packetized elementary stream (PES) refers to the MPEG PES. The term MPEG denotes MPEG-1, MPEG-2, MPEG-4, MPEG-7 and other MPEG standard formats having the same or similar MPEG-2 stream, packet and field structures. The term MPEG also denotes a DDS stream, in which the stream, packet and field structure is the same or similar to that of MPEG-2, but has a different name.

FIG. 1 is a schematic diagram of a receiver according to a first embodiment of the present invention; in FIG. 1 , the receiver 100 includes a descrambler 105, a demultiplexer 110, a storage subsystem 115, an audio decoder and presenter 120, Video decoder and display 125, clock oscillator circuit 130, recording STC 135, playback STC 140 and frequency adjustment circuit 145. Storage subsystem 115 includes write controller 150 , storage medium 155 and read controller 160 .

In operation, an encrypted transport stream (TS) 165 is received by decryptor 105 and decryptor 105 outputs a decrypted transport stream 170, which is received by demultiplexer 110 at the rate at which encrypted transport stream 165 is broadcast . PLL circuit 130 generates fixed frequency signal 175 which is sent to recording STC 135 and frequency adjuster 145. The recording clock signal 180 generated by the recording STC 135 is received by the demultiplexer 110 and the write controller 150. The demultiplexer 110 extracts the value of the first PCR field in the first header of the decrypted transport stream and calculates the encoder system time clock frequency (the clock used to establish the original value in the SCR field of the program stream and in the transport stream The X offset between the original value established in the PCR field of ) and the frequency of the recorded STC 135. This operation can be expressed as X-axis offset=first PCR-record STC.

Demultiplexing 110 converts the decrypted transport stream 170 into an audio elementary stream (AES) 185 and a video elementary stream (VES) 190 . AES 185 and VES 190 are PES formats. The decrypted transport stream 170 can also be decomposed into other streams besides audio and video, such as teletext. These other streams will be treated equally as AES 185 and VES 190. Demultiplexer 110 adds an X offset to one or more original PTS field values PTS to create a new value PTS1 in the PTS field of AES 185 and VES 190 and writes PTS1. Demultiplexer 110 also adds an X offset to one or more original DTS field values DTS to create a new value DTS1 in one or more DTS fields of AES 185 and VES 190 and writes DTS1. These two operations can be expressed as PTS1 = PTS + X offset and DTS1 = DTS + X offset. AES 185 and VES 190 and recording STC frequency signal 195 are sent to write controller 150 of storage subsystem 150. Record STC frequency signal 195 carries the frequency value of record STC 135 when calculating the X offset.

Write controller 150 interleaves all elementary stream information (AES 185, VES 190, frequency signal 195) related to the same time as a single segment and stores the segment on storage medium 155.

The receiver 100 can play programs in two modes, a live playback mode or a delayed playback or time-shifted recording (TSR) mode. Programs are not stored in live playback mode. In live playback mode, the receiver 100 "hotwires" the AES 185 to the audio decoder and presenter 120, and the VES 190 to the video decoder and presenter 125, as indicated by the dotted lines . The Video Decoder and Presenter 125 acts as a "host" and, based on the time of recording the STC 135 and the PTS field (including the value PST1 ) and DTS field (including the value DTS1 ) of the AES 185 and VES 190, receives data from the demultiplexer 110 Pull segments.

The program is stored in delayed play mode and played back under the control of the storage subsystem 115 . For the delayed playback mode, the read controller 160 stored in the system 115 reads and sends the stored frequency signal 195 to the frequency adjuster 145, which adjusts the fixed frequency signal 175 to match the stored frequency signal 195 and output the adjusted fixed frequency signal 196. Adjusted fixed frequency signal 196 is received by playback STC 140 which sends playback clock signal 197 to audio decoder and display 120, video decoder and display 125, and readout controller 160. Thus, when the program is demultiplexed, the playback STC 140 operates at the same frequency as the recording STC 135.

For the delayed playback mode, the read controller 160 calculates the storage offset (S offset), which is the difference between the pause time (TP) according to the play STC 140 and the resume time (TR) according to the play STC. These operations can be expressed as S offset = TR - TP. Read controller 160 adds the S offset to one or more current PTS field values PTS1 to create a new value PTS2 in that PTS field for AES 185 and VES 190 and writes PTS2. Read controller 160 also adds an S offset to one or more current DTS field values DTS1 to create a new value DTS2 in that DTS field for AES 185 and VES 190 and writes DTS2. These two operations can be expressed as PTS2 = PTS1 + S offset and DTS2 = DTS1 + S offset. Video decoder and presenter 125 acts as a "host" and pulls segments from storage subsystem 115 at the rate represented by the storage subsystem.

FIG. 2 is a schematic diagram of a receiver according to a second embodiment of the present invention; in FIG. 2, the receiver 200 includes a decryptor 205, a transmit packet selector 210 based on a packet identifier (PID) (hereinafter referred to as selector 210) , storage subsystem 215, demultiplexer 217, audio decoder and display 220, video decoder and display 225, clock oscillator circuit 230, free running clock 235, playback STC 240 and frequency adjustment circuit 245. Storage subsystem 215 includes write controller 250 , storage medium 255 and read controller 260 . Read controller 260 includes optional injector 262 . Injector 262 may be a hardware or software injector.

In operation, encrypted transport stream 265 is received by decryptor 205 , and decryptor 205 outputs decrypted transport stream 270 , which is received by selector 210 at the rate at which encrypted transport stream 265 is broadcast. PLL circuit 230 generates fixed frequency signal 275 which is sent to clock 235 and frequency adjuster 245 . Clock signal 280 generated by clock 235 is received by selector 210 and write controller 250 . Selector 210 extracts packets from decrypted transport stream 270 based on the selected program or programs. The selection is based on the value corresponding to the selected program in the PID field of each packet header in the decrypted transport stream. Selector 210 adds a four byte time stamp at the beginning of each selected packet to generate partial transport stream 282 which is received by write controller 250 of memory subsystem 215 . Write controller 250 places the partial transport stream into storage medium 255 .

The receiver 200 can play programs in two modes, live playback mode or delayed playback or TSR mode. In the live play state, as indicated by the dashed line, no program is stored and the receiver 200 "hotwires" the selector 210 to the demultiplexer 217 and sets the S offset (described below) to zero.

In delayed play mode, the program is stored in memory subsystem 215 . For delayed play mode, the demultiplexer 217 performs several operations now described. The order in which the operations are described is not necessarily the order in which the operations are performed.

There are two options for sending the partial transport stream 282 from the memory subsystem 215 to the demultiplexer 217 . In the first or "push" option, the injector 262 reads the four byte timestamp and "injects" each packet into the demultiplexer 217 at the appropriate time. In the push option, the demultiplexer 217 removes the four byte time stamp from each packet as it is received. In the second or "pull" option, the injector 262 is not used (or not present), and when the demultiplexer 217 receives it, it reads and removes four bytes of time stamp. The Video Decoder and Presenter 225 "pulls" video based on VES consumption. When the amount of VES data in the buffer (not shown) of the video decoder and presenter 225 is below a threshold, the video decoder and presenter "pulls" more data from the demux 217 .

The demultiplexer 217 calculates the storage offset (S offset), ie the difference between the value of the first PCR field in the first header of the partial transport stream 282 and the current playing STC 240 time. This operation can be expressed as S offset=first PCR-play STC.

The demultiplexer 217 converts the decrypted partial transport stream 282 into an AES stream and a VES stream. AES and VES streams are in PES format. The decrypted partial transport stream 282 may also be decomposed into streams other than audio and video, such as teletext.

For each PES in AES and VES, the demultiplexer 217 adds the S offset to the current one or more PTS field values PTS to create a new value PTS3 and writes PTS3 to the PTS of AES and VES. One or more PTS fields. For each PES in AES and VES, the demultiplexer 217 adds the S offset to the current one or more DTS field values DTS to create a new DTS value DTS3 and writes DTS3 into the AES and VES One or more PTS fields of the VES. These two operations can be expressed as PTS3 = PTS + S offset and DTS3 = DTS + S offset.

The demultiplexer 217 uses the PCRs with the partial transport stream 282 and the four byte time stamps of the arriving transport packets to calculate and set the frequency at which the STC 240 is played via the frequency adjuster 245, which divides the fixed frequency signal 275 to adjusted fixed frequency signal 296 . The adjusted fixed frequency signal 296 is received by the playback STC 240, which sends the playback clock signal 297 to the demultiplexer 217, the audio decoder and displayer 220, and the video decoder and displayer 225. These operations are fully disclosed in the aforementioned related application "RobustMethod For Recovering A Program Time Base In MPEG-2 TransportStreams And Achieving Audio/Video Synchronization" S/N09/967,877. Thus, the operating frequency of the playback STC 240 is the same as the program clock when the program stream was established.

The video decoder and presenter 225 acts as a "host" and pulls segments from the storage demux 217 at the rate indicated by the demux.

When the user of the present invention puts receiver 100 or receiver 200 into trick-play mode (i.e., fast forward, fast reverse, slow forward, slow reverse, or pause), the video stored on storage medium 155 or storage medium 255 is The rate representation of , and there is no audio or the audio does not need to be synchronized with the video. In this case, for both embodiments of the invention, the storage offset is set to zero and either the STC 140 or the playback STC 240 can run at the last set frequency.

After trick play mode, when the user of the present invention restores receiver 100 or receiver 200 to normal play mode (real-time play and delayed play are normal modes), the resulting situation can be considered as a discontinuity in the time base . In this case, for both embodiments, the current PTS value in the PTS field of each PES packet is adjusted based on the new offset. The new offset is a function of the PTS field value and the current value of the Play STC 140 or Play STC 240. For the first embodiment of the present invention, it can be expressed as PTS4=PTS1+new offset, and for the second embodiment of the present invention, it can be expressed as PTS5=PTS+new offset. The determination of the new offset is fully disclosed in the aforementioned related application "Robust Method For Recovering A Program Time Base InMPEG-2 Transport Streams And Achieving Audio/Video Synchronization" S/N 09/967,877.

Figure 3 is a graph illustrating the relationship between receiver playback and recording STC and PTS modified according to the present invention during recording; 1), or the time as seen by the audio decoder and presenter 220 and the video decoder and presenter 225 (see FIG. 2 ), the horizontal axis is actual time. As shown in FIG. 3, the values of the play STC and record STC curves 300 increase linearly at a fixed rate. The PTS curve 305 represents the PTS value increment required within AES and VES to avoid video or audio discontinuity in the represented program. The slope of the PTS curve 305 must be the same in slope, although it may be offset in decoder time from the play STC and record STC curves 300 . The PTS curve 310 represents the recorded PTS values of AES and VES (or, in the case of the second embodiment, the PTS values of AES and VES obtained from stored partial transport streams). In first portion 315 of PTS curve 310, PTS curve 310 overlaps PTS curve 305 and accurately times the audio and video represented. Section 315 is live playback. In the second portion 320 of the PTS curve 310, the program is paused and treated as if a discontinuity had occurred. As long as the program is paused, the PTS value in section 320 is not incremented, and there is an offset 330 between PTS curve 305 and PTS curve 310 when playback continues according to third section 325 of PTS curve 310 . The slopes of the PTS curves 305 and 310 are the same, but they are offset in decoder time. The offset 330 is due to the time taken in the pause (store) process, and the present invention corrects the offset 330 by adjusting the PTS value to compensate for the store time as described above. The curves for DTS values will be similar to their corresponding PTS values.

Fig. 4 is a graph illustrating the relationship between receiver playback and recording STC, original PTS and PTS modified according to the present invention during trick-to-normal play. In FIG. 4, the vertical axis is audio decoder and presenter 120 and video decoder and presenter 125 (see FIG. 1), or audio decoder and presenter 220 and video decoder and presenter 225 (see FIG. 2). Seeing time, the horizontal axis is actual time. As shown in FIG. 4, the values of the play STC and record STC curves 400 increase linearly at a fixed rate. PTS curve 405 represents the increment of PTS value required within AES and VES to avoid video or audio discontinuity in the represented program. The slope of the PTS curve 405 must be the same in slope, although it may be offset in decoder time from the play STC and record STC curves 400 . The PTS curve 410 represents the recorded PTS values of AES and VES (or, in the case of the second embodiment, the PTS values of AES and VES obtained from stored partial transport streams). In a first portion 415 of the PTS curve 410, the PTS curve 410 overlaps the PTS curve 405 and accurately times the audio and video represented. Section 415 is live playback. In the second portion 420 of the PTS curve 410, the program is paused and treated as if a discontinuity had occurred. The PTS value in section 420 is not incremented as long as the program is suspended. There is an offset 430 between the PTS curve 405 and the PTS curve 410 as playback continues according to the third portion 425 of the PTS curve 410 . The slopes of the PTS curves 405 and 410 are the same, but they are offset in decoder time. The offset 430 is due to the time taken in the pause (store) process, and the present invention corrects the offset 430 by adjusting the PTS value to compensate for the store time as described above. In the fourth portion 435 of the PTS curve 410, a trick play is performed, which in this embodiment is fast forward and is treated as a discontinuity. In the fourth portion 435 of the PTS curve 410, the timing does not need to be maintained due to the nature of the trick-play distortion timing. However, there is an offset 440 between the PTS curve 405 and the PTS curve 410 after exiting the trick play mode as indicated by the fifth portion 445 of the PTS curve 410 . The slopes of the PTS curves 405 and 410 are the same, but they are offset in decoder time. Offset 440 is due to delay distortion caused by trick play, and the present invention also corrects offset 440 by adjusting the PTS value to compensate for storage time as described above. The curves for DTS values will be similar to their corresponding PTS values.

The present invention can be understood by the embodiments of the present invention described above. It should be understood that the present invention is not limited to the specific embodiments described herein, and those skilled in the art can obviously make various modifications, reconfigurations and substitutions thereto without departing from the present invention. It is therefore intended that the following claims cover all such modifications and changes as fall within the true spirit and scope of the invention.

Claims (20)

1. a receiver is used to receive MPEG encrypted transport stream and output audio and vision signal, comprising:

Decipher is suitable for receiving encrypted transmission stream, and the transmission stream of decrypt encrypted is also exported decrypted transmission stream;

Demultiplexer, be suitable for receiving decrypted transmission stream, being suitable for that decrypted transmission circulation is changed to audio frequency flows and video-frequency basic flow substantially, and be suitable for changing audio frequency and flow substantially and the express time mark of each header of each grouping of video-frequency basic flow and the value in the decoding time mark field time, and be suitable for output audio and flow substantially and video-frequency basic flow with coupling receiver recording clock;

Storage subsystem, being suitable for reception and storing audio flows and video-frequency basic flow substantially, and be suitable for changing audio frequency and flow substantially and the express time mark of each header of each grouping of video-frequency basic flow and the value in the decoding time mark field, flow substantially with video-frequency basic flow with compensating audio and be stored in time quantum in the storage subsystem;

Audio decoder is suitable for receiving the decode audio frequency and flows substantially and be suitable for output audio signal; With

Video Decoder is suitable for receiving the decode video-frequency basic flow and is suitable for outputting video signal.

2. receiver according to claim 1 also comprises frequency adjusting device, is used to adjust the frequency that receiver is play clock, with the frequency of coupling receiver recording clock.

3. receiver according to claim 2, wherein, storage subsystem when Voice ﹠ Video when stream is stored in the storage subsystem substantially receiver play each express time tag field and each decode time tag field that the memory time of difference between the reproduction time on the receiver broadcast clock when stream is read out storage subsystem substantially when Voice ﹠ Video on the clock is added each header of each grouping of Voice ﹠ Video in flowing substantially to.

4. receiver according to claim 1, wherein, demultiplexer the value of the first program clock reference field of the header of the relevant grouping of decrypted transmission stream neutralization program to be stored and the difference of the current time of receiver recording clock add to Voice ﹠ Video flow substantially in each express time tag field and each decode time tag field of each header of each grouping.

5. receiver according to claim 1, wherein, demultiplexer be suitable for directly audio frequency substantially stream be input to audio decoder and directly video-frequency basic flow be input to Video Decoder.

6. a receiver is used to receive MPEG encrypted transport stream and output audio and vision signal, comprising:

Decipher is suitable for receiving encrypted transmission stream, deciphers this encrypted transmission stream and exports decrypted transmission stream;

Selector, be suitable for receiving decrypted transmission stream, be suitable for selecting the grouping relevant with one or more programs, and be suitable for setting up the part that includes only the grouping relevant and transmit with one or more programs, be suitable for adding time mark to each grouping that partly transmits in the stream, and be suitable for output transmission stream based on the receiver recording clock;

Storage subsystem is suitable for receiving and storage area transmits stream;

Demultiplexer, be suitable for receiving unit and transmit stream, being suitable for that part transmission circulation is changed to audio frequency flows and video-frequency basic flow substantially, be suitable for changing audio frequency and flow substantially and the express time mark of each header of each grouping of video-frequency basic flow and the value in the decoding time mark field, transmit stream with compensated part and be stored in time quantum in the storage subsystem;

Audio decoder is suitable for receiving the decode audio frequency and flows also output audio signal substantially; With

Video Decoder is suitable for receiving the decode video-frequency basic flow and outputting video signal.

7. receiver according to claim 6 also comprises frequency adjusting device, is used to adjust receiver and plays the frequency of the frequency of clock with coupling receiver recording clock.

8. receiver according to claim 7, wherein, this frequency adjusting device transmits the express time marker word segment value of each packet header in the stream and the currency that receiver is play clock based on part, adjusts the frequency that receiver is play clock.

9. receiver according to claim 6, wherein, demultiplexer first program clock reference field value of the header of the relevant grouping of decrypted transmission stream neutralization program to be stored and the difference of receiver recording clock current time add to Voice ﹠ Video flow substantially in each express time tag field and each decode time tag field of each header of each grouping.

10. receiver according to claim 5, wherein, selector is suitable for that part is transmitted stream and is directly inputted to demultiplexer.

11. receiver according to claim 6, wherein, storage subsystem is injected grouping based on the time mark that is added in each grouping of part transmission stream.

12. a method is used for making the audio ﹠ video of mpeg decoder synchronous, comprising:

Deciphering transmits stream;

Separate multiplexed transmission stream;

From transmit stream, extract the value of the first program clock reference field in the header of first grouping relevant with program;

To transmit stream separates and is multiplexed as audio frequency and flows substantially and video-frequency basic flow;

Difference between the first program clock reference field value in the header of the grouping that the current time is relevant with decrypted transmission stream neutralization program to be stored add to the Voice ﹠ Video relevant with program to be stored flow substantially in each express time tag field and each decode time tag field of each header of each grouping;

Storing audio and video-frequency basic flow;

When reading Voice ﹠ Video and flow substantially, the difference between time when stream is stored substantially when Voice ﹠ Video and the reproduction time when from memory, reading Voice ﹠ Video and flow substantially add to Voice ﹠ Video flow substantially in each express time tag field and each decode time tag field of each header of each grouping; With

Decoded audio and video-frequency basic flow.

13. method according to claim 12 also comprises:

Adjust the frequency of the frequency of reproduction time with the matched record time.

14. method according to claim 12 also comprises:

When after having changed the common read-out speed that Voice ﹠ Video flows substantially, continuing common read-out speed, with add to based on the skew of the express time marker word segment value of the basic stream packets header of audio frequency and video-frequency basic flow packet header and current reproduction time Voice ﹠ Video flow substantially in each express time tag field and each decode time tag field of each header of each grouping.

15. the synchronous method of Voice ﹠ Video that is used for making mpeg decoder comprises:

Deciphering transmits stream;

The part of selecting grouping relevant with one or more programs and foundation to include only the grouping relevant with described one or more programs transmits stream;

Each header that part transmits each grouping in the stream will be added to based on the time mark of current record time;

Storage area transmits stream;

Reading section transmits stream;

To partly transmit stream separates and is multiplexed as audio frequency and flows substantially and video-frequency basic flow;

First program clock reference field value in the header of the grouping that decrypted transmission stream neutralization program to be stored is relevant and the difference between the current time add to Voice ﹠ Video flow substantially in each express time tag field and each decode time mark of each header of each grouping; And

Decoded audio and video-frequency basic flow.

16. method according to claim 15 also comprises:

Adjust the frequency of the frequency of reproduction time with the matched record time.

17. method according to claim 16 wherein, transmits the express time marker word segment value and the current reproduction time of each packet header in the stream and adjusts this frequency based on part.

18. method according to claim 15 also comprises:

When after having changed the common read-out speed that Voice ﹠ Video flows substantially, continuing common read-out speed, with add to based on the skew of the express time marker word segment value of the basic stream packets header of audio frequency and video-frequency basic flow packet header and current reproduction time Voice ﹠ Video flow substantially in each express time tag field and each decode time tag field of each header of each grouping.

19. method according to claim 12 wherein, selects to be based on that the program id field value that transmits packet header in the stream carries out.

20. receiver according to claim 12, wherein, the speed that reads from Voice ﹠ Video flows substantially is based on and is added to the time mark that part transmits the header of each grouping of stream.

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